Process for making building products, production line, process for firing, apparatus for firing, batch, building product

ABSTRACT

A method for making a building product from products of firing a clay-containing material and products of processing a lime-releasing material. The method comprises firing at least a clay-containing material up to at least beginning of its sinter, obtaining a molding mix comprising lime and products of firing a clay-containing material, molding a body of building product from the mix, and treating the body in a humid medium or in a medium containing water vapor. The products of firing a clay-containing material include a mixture of first and second portions that have been heated to respective first and second temperatures that are different from one another, the two different temperatures being within the temperature range from a temperature of beginning of dehydration to at least a temperature of sinter of clay, so that the products of firing comprise both products of dehydration and products of amorphization of clay.

The invention relates to the manufacture of building materials and maybe used for making wall and other building products, e.g., brick andwall panels, preferably out of clayey raw materials. It can also be usedfor preparing batch mixtures, mortars and for other uses.

STATE OF THE ART

Most valuable building products from the point of view operationalcharacteristics and architectural and aesthetic properties are ceramicbrick or stones of clayey raw materials which are produced by preparinga raw material molding green body, drying it at 100° to 150° C. during 2to 4 days, and firing at 900° to 1100° C. during 2 to 3 days. Forproducing, lining brick, either monomineral clays or loams have to beused, or clayey raw material should be homogenized and stirred whichcalls for high energy consumption with rather bulky productionequipment. Inclusions of limestone or dolomite of a size larger than 1to 2 mm in an amount exceeding 1 to 3% in this process are inadmissibleas they result in destruction of fired bricks upon wetting. Longduration of firing is necessary to ensure curing of the brick duringseveral hours under conditions where the brick surface is heated to atemperature not above the upper limit of the sintering range and thepoints most distant from the surrface of the brick are heated to atleast the lower limit of the sintering range. The long time periods fortemperature rise and temperature decrease during firing are necessary toavoid defects. These features result in a protracted production cyclelasting for at least 10 to 15 days, high thermal energy consumption fordrying and firing, high material usage and cost of production equipmentand as a result high brick cost.

Lower duration of production processes is characteristic of processesmaking use of the hydraulic hardening mechanism instead of pyrosilicatehardening. The main of these processes are as follows.

Processes of making silica brick, stones, and silica-concrete blocksinvolves forming green body from humidified mixture of quartz sand andlime, generally without adding other binders; autoclaving the resultinggreen body under saturated steam pressure of 0.8 to 1.6 MPa at 175° to200° C. during 7 to 12 hours. These processes are characterized by theneed to prepare lime in lime kilns, the need to use sand without harmfulinclusions, e.g., clayey inclusions. In the majority of applicationsquartz sand is to be ground completely or in part. These processes areaccompanied by dust. In addition to said features, these processes arecharacterized by necessity of employment the autoclaves and steam ofhigh parameters. These lime-silica products have low aesthetic valuedeteriorating during operation. This is why constructions made fromsilica brick are either painted or lined. In silica brick, similarly toceramic brick, cohesion with mortar deceases with an increase offrost-resistance, and vice versa since these parameters depend onaccessible porosity on the product surface.

Building products are also manufactured on the basis of cement binders,e.g., Portland cement. Cement-based products are capable for hardeningboth under autoclaving and at normal temperature. However, preparingcement is associated with high fuel consumption for firing raw meal attemperatures about 1500° C. and with high energy requirements for finegrinding both carbonate and clayey raw materials and very strong clinkeras firing product. Production and application of cement are associatedwith a strong dust lading of air. Production equipment is characterizedby a high material usage, especially for the construction of linedkilns. Cement-based products are also of a low aesthetic value if usedwithout supplementary finishing.

In addition to said processes, known in the art are other processesinvolving the use of compositions or components containing clayey rawmaterials or products of their processing:

it is known that 1! clays and loams are hydraulically active in thepresence of lime only under autoclaving conditions and are inactive atnormal temperature;

it is known that 1! finely ground burnt rocks, fuel ashes, and clayeycomponents of brick cement (products of clay firing at a temperaturebelow 800° C.) are active in the presence of lime both under autoclavingand at normal temperature;

it is known that 2! clayey rocks fired at 500° to 600° C. are mostactive, and those fired at 800° to 1000° C. are much less active;

lime and burnt-clay binders (brick cements) are also known 2,3!;

lime and slag binders are known 1! which contain a substantial amount ofvitreous aluminosilicates;

lime and belite binders 3! are prepared by firing at 1000° C. to 1200°C. natural or artificial limestone and silica or limestone and claymixtures;

Portland cements with mineral additives are known 1,3!, the additivebeing in form of burnt rocks and ashes.

All the above mentioned binders should be finely ground which causestheir high water demand. They change in volume under hardening. Loweringwater demand and smaller dimensional changes achieved by adding normalaggregates (as in the case of cement-based concrete) cannot be used forhardening without autoclaving since no-cement binders do not react withgenerally used aggregates of any particle size. Besides, this isinefficient.

It is known to prepare chamotte and lime products 4! by using clay andlimestone firing at 950° to 1000° C. wetting firing products and finelygrinding them, forming a product and autoclaving it under 0.8 to 1.6MPa. One of the embodiments of this process involves adding to 10 to 30%of nonfired clay which is assumed to cause an increase in density ofgreen body and finished product, a decrease in open porosity, andenhancement of frost-resistance. In another embodiment of this process,nonfired clay or a part of it is added in the form of slip.

Known in the art is a production line 5! for carrying out this process,with burn-out additives introduced into a mixture of clay and limestonefired in a rotary kiln.

This process 4,5! is used for making products similar to silica brick.Quartz sand here is replaced by finely ground ceramic sand, and a binderis in form of lime, raw clay, and comminuted ceramic fines. This processallows a product to be obtained with heightened frost-resistance andwith high aesthetic value identical to that of lining ceramic bricksince the raw material is repeatedly homogenized and stirred duringproduction cycle. This process allows undergrade clayey raw materialwith high content of coarse carbonate inclusions up to 20% and greaterto used which cannot be used in the conventional ceramic productionprocesses. This process lowers energy consumption and material usage forthe construction of equipment owing to a reduction of the cycle durationto 20 to 30 hours. In addition, there is no dust lading of the air inusing this process. This process seems to be most similar to claimedinventions.

At the same time, this process 4,5! has certain fundamental distinctionsincluding the need to use a lined rotary kiln with high dust losses andsubstantial fuel consumption, emissions of sulfurous compounds availablein both raw materials and fuel. This process also calls for autoclavingwith normal pressure of about 0.8 MPa. All this results in high materialusage of equipment and high energy requirements.

The need of autoclaving with high steam parameters is caused by the factthat aluminosilicate components of the binder, namely, nonfired clay andceramic sand (product of firing at 1000° C.) are active enough in thepresence of lime only under autoclaving.

State of the art shows the following: all processes for making buildingproducts and mortars are characterized by the fundamental feature,namely, by the use of kilns which are lined for a temperature of atleast 1000° C.; a number of processes in making hydraulically hardeningproducts are characterized by the use of autoclaves with high-parametersteam; high material usage of equipment and high power requirementsassociated with mentioned above and other features of the processes.

The claimed inventions are aimed at bringing solutions of the followingproblems:

lower material usage of equipment and energy consumption owing to:preparation of batches and manufacture of products for which autoclavingand high-parameter steam are not necessary for hardening; elimination ofthe need to use lined kilns at all stages of the production process.

enhanced operation properties of products, including: architectural andaesthetic properties, frost resistance, cohesion with mortar.

SUMMARY OF THE INVENTION

The common inventive concept of the inventions claimed here resides, inthe first place, in the fact that a batch for preparing hydraulicallyhardening building products contains products of different-temperatureprocessing of raw materials; the raw materials consisting of, orcontaining a clayey or a clay-like component; and by this fact theelimination of the need to use autoclaves and high-parameter steam isreached. This approach is based on the following.

During heating, chemical and physical and chemical processes occur in aclayey substance which develop in minerals proper and in admixtures, aswell as a result of reactions of products of decomposition ofclay-forming minerals with admixtures and products of decomposition ofadmixtures. The following processes among those are decisive for ourcase:--oxidation of natural organic substances at 300° to 400°C.;--turning of oxide iron form to ferrous oxide, which is highlyreactive, beginning with 350° to 500° C. in particular, under the effectof carbon from admixtures;--dehydration of clayey minerals begins at450° to 600° C., with the elimination of chemically bound water, and thematerial acquires high chemical activity, with some hydroxyl groupsstill remaining in the material; --the dehydrated product startsdecomposing with the release of amorphous silica at 700° to 800°C.;--crystal lattice of the minerals is broken at 880° to 950° C., inthe exothermal effect area, with the removal of hydroxyl groups,formation of free oxides, rearrangement of the lattice, breakage of thelayer of tetrahedrons, and partial change the coordination ofions;--primary eutectics (beginning of sinter) are formed, generally,from 700° to 900° C. owing to the admixtures;--at higher temperatures,generally above 900° to 950° C., formation of primary mullite begins(partial sinter) as a result of which the product becomes waterresistant, frost resistant and strong formation which is actuallypresent in the body of conventional ceramic brick;--further increase oftemperature above 1100° to 1200° C. results in a beginning of melt beingformed (complete sinter);--if there are oxides of alkali metals such ascalcium oxide or their carbonates in the clayey raw material, calciumaluminates, aluminoferrites and silicates are formed beginning with 900°C. The actual picture is more complicated; mentioned effects occur atdifferent temperatures in different clayey minerals with differentadmixtures. They, however, generally take place within the abovementioned temperatures.

The most hydraulically active among products of heating of clayeysubstance are: products of dehydration; free iron oxides; products ofamorphization as products of heating at 880° to 950° C., but not up tosintering, which can be active even without presence of lime or cement.Properties of the products of hardening may be improved by adding to themolding mass an admixture of a ceramic phase (a product of firing at900° to 1100° C.) of a certain particle size, preferably with an optimumgrading factor which ensures the most dense packing. The surfaces ofcleavage of the ceramic phase have a high open porosity which is theresult of the internal porosity of the intact ceramic phase. The pillarsbetween open pores terminating in the cleavage surface are very activeunder non-autoclaving conditions. This high activity only takes place incontact with a substance which is active under normal conditions and notonly under autoclaving. This is also due to the fact that cleavage ismost likely to take place at the vitreous phase which is less strongthan the crystalline newly formed structures and is hydraulically moreactive.

Activity of batch for molding according to this invention is enhancedadditionally thereof in a case when the different-temperature phases areavailable in it, and in the first place, products of dehydration (about500° to 600° C. and up to 800° C.) and products of amorphization (about880° to 950° C.) since these components have, as shown above, differentmechanisms of physical and chemical surface activity, and thereby theircontact with each other is most effective in comparison with asingle-temperature phase which results in an increase in density,strength and frost resistance of the product and also allows moldingmoisture content to be lowered.

Thereby, from the above, the best batch for making products is the onecontaining fine dehydrated and amorphous phases and a ceramic filler ofdifferent particle sizes, as well as an alkaline additive as a bindercomponent, e.g., lime. A mixture containing two of the above mentionedaluminosilicate components may also be used.

The content of each component in the batch may vary:

if a non-finely divided ceramic component (aggregate) is available inthe mixture, the content of rest of components depends on the volume ofvoids between the grains of the aggregate and may range from 10 to 40%;

in case there is no ceramic or other aggregate in the mixture (which isalso true of finely divided phases in the former case with theaggregate), the amount of an alkaline additive in the finely-dividedphase may vary from 10 to 60% depending on the desired properties of thefinished product and fineness of each component. With an optimum gradingfactor of the aggregate, it may be as low as 2%;

if there are both amorphous and dehydrated components in the mixture,the amount of each of them may largely vary.

If each of different-temperature phases is a product of thermaltreatment of one and the same clayey mineral, this will give anadditional result since when calcium hydroaluminosilicates are formed,as well as other formations, distortions of silicon and oxygen elementsand other components of the structure either disappear or are negligibleso that the height of a thermodynamic barrier hindering the developmentof the chemical reactions between the components is lowered.

This approach allows to prepare a batch with substantially lower cost ofthermal treatment of raw materials, and this batch may be used, asdistinguished from prior art 4,5!, for making products hardening underhumid conditions or in a medium containing water vapor either at normaltemperature, or under steaming at normal pressure, or under autoclavingwith a substantial reduction of autoclaving duration. All this resultsin a lower material usage for making production equipment and a decreasein power requirements.

If a carbonate, e.g., limestone is available in, or added to clayey rawmaterials, the fired product will contain highly active formations aswell, which are characteristic of cement, however it is unnecessary toadd cement.

The batch for molding may also contain up to about 5 to 15% of nonfiredclayey phase. Being plastic and finely divided, clayey phase enhancesmoldability of the mixture, increase density and improve othercharacteristics of the product, but the availability of and increase inthe content of this clayey phase call for an increase in the humidtreatment temperature.

A new composition of batch for molding according to the invention has,in addition to above mentioned useful properties, other valuabledistinction:

products prepared from these compositions have improved cohesion witmortar owing to chemical reactions between dehydrated and/or amorphousphases available on the product surface and Portland cement of themortar, in particular, calcium hydroxide released as a result ofhydration of Portland cement of the mortar;

finely divided phases, and in the first place, dehydrate have, incomparison with ceramic phase, and the more so with raw clay, a muchmore intense color owing to dyeing with iron oxides so as to enhancearchitectural and aesthetic properties of products;

products or mortars consisting of, or containing a mixture ofdifferent-temperature phases have enhanced frost resistance owid to thefollowing factors:--possibility of lowering of molding moisturecontent;--possibility of lowering of open porosity of products by usinghumid thermal treatment under atmospheric pressure or under a lowsurplus pressure to replace autoclaving, because autoclaved product areknown to have long open pores and capillaries which are formed at theend of the autoclaving owing to intensive migration of moisture withinthe product towards its surface.

These properties are inherent in cement-based concrete if the mixtureaccording to the invention is added as an additive to a concrete.Resistance of such concrete in a number of aggressive media is higherthan when pozzolana or slags are added.

A mixture of different-temperature phases may be obtained by mixingcomponents prepared individually at respective temperatures. Anadditional lowering of power requirements may be achieved by using heatreleased in preparing a higher-temperature phase for thermal treatmentwith the aim of preparing another or other temperature phases, e.g.,gases exhausted from rotary kiln for dehydration of respective part ofclayey raw materials, e.g., in a high-temperature drier.

Lime or another alkali-containing or alkali releasing component may beadded to batch for molding after firing the clayey component. It isbetter to make use of a step of the prior art process 4,5! in which anatural or artificial mixture of clay and limestone is fired.

Separate preparation of different-temperature phases is worse from themanufacturing point of view since it calls for the use of severalthermal units. Further decrease in weight of production equipment andrational heat utilization may be obtained by firing all clayey or clayeyand carbonate raw materials in one and the same unit, by providing anon-stationary temperature field in the mass of raw materials, with apreset temperature gradient. This approach may be implemented, e.g., bysupplying the mass of raw materials into a slit-type tunnel kiln or to ashaft furnace having gas or other burners placed along the perimeter ofits middle part. The temperature gradient is thus directed to the zoneoutside the raw material mass, and thermal flux is directed into theinterior of the raw material mass. As a result of such firing, itsproduct will be in the form of mixture of different-temperature phases.

Solution of second of main problems, namely elimination of the need touse lined kilns, is achieved by creating in the mass of raw materials anon-stationary temperature field with a temperature gradient directedinto the interior of the raw material mass, by directing the thermalflux from the interior of raw material mass to outside of the rawmaterials. This step can be implemented by heating the interior of thefired mass up to a maximum temperature of, e.g., up to 900° to 1100° C.,and so as the outer part of the mass transforming in the form ofdehydrated clay, or non-dehydrated dried clay; it results in rejectingheat-resistant lining and replacing it with a thin casing, e.g., of ametal sheeting which can also be eliminated with in certainapplications. As will be shown later, it is preferred to implement thisstep by heating the interior of the raw material mass placed in a shaft(similar to a shaft furnace). A heat carrier, e.g., a gas can beintroduced into the central part of the shaf. If a solid fuel is used orthe use is made of a raw material containing a solid fuel component suchas wastes of coal recovery or thermal utility wastes, it is morepreferably to place the fuel-containing raw material into the centralpart of the shaft cross-section, and a raw material that does notcontain a solid fuel component is placed in the zones adjacent to theshaft walls.

Placing a clayey component in the wall zone of the shaft lowers a wearof the shaft during its operation since nonfired or dehydrated clay hasa low hardness which is also important in making use of a conventionalshaft furnace for carrying out the process according to the invention.

If a solid fuel component is available in the raw mixture, introducingair into the area of the mixture which is at the maximum temperature orinto the area of the firing zone adjacent to the heating zone ensures anadditional protection of the shaft against thermal influence and alsoprovides for afterburning of carbon oxide and lowering of its emissions.

In the prior art process 5! firing is carried out in countercurrentwhich has its manufacturing advantages. However, since sulfur isavailable in fuel and/or in burning additives, sulfur dioxide isreleased into atmosphere, and the release of sulfur dioxide from thesolid fuel component begins, generally, in the preheating zone. Thiscomponent is removed from the kiln together with other gases. Firing ofclayey, carbonate and solid fuel granules by said method lowersemissions of sulfur dioxide, but this reduction is insignificant. If thefiring is carried out in co-current in a rotary kiln or in a shaftfurnace or/and firing products are placed, before molding of a product,in off gases of the furnace, the reaction between sulfur dioxideavailable in the gases with lime which is reactive towards such gasesresults in the formation of calcium and/or magnesium sulfates, i.e.,gypsum. The presence of gypsum in the mass for molding enhancesstrength, frost resistance and air resistance of the product,accelerates hardening or gives additional lowering the parameters ofhumid thermal treatment.

Green body may be molded by any appropriate method including pressing,tamping, vibration, rolling, and by other methods. Product quality isenhanced when molding is carried out under vibratory conditions as theceramic phase of the fired products have a large number of open pores.By vibrating of humid molding mass, a moisture gets out of open pores,an intensive stirring of components takes place and humid mass fills upthe pores again when the vibratory treatment is suspended.

Fired products are subjected to fine comminution (grinding) in the priorart processes 4,5!. This mixture has a high final porosity because of ahigh molding moisture content and other disadvantages. It is preferredthat ceramic phases act as a aggregate with an optimum grading factor,the rest of the phases being comminutes to fractions smaller than 0.1 to0.2 mm; i.e., it is preferred that the fired products be partlycomminuted. This can be achieved by combined comminution of allcomponents with the attainment of the desired fineness of nonceramicphases owing to the abrasive effect of a harder ceramic component. Themajority of prior art apparatuses for comminution of materials ensurecomminution which is selective in terms of strength and hardness. Rotarycrushers are known to provide maximum selectivity. Different phase arepreferably comminuted separately, e.g., a ceramic product of firing to asize smaller than 5 to 10 mm and dehydrated and amorphous phases by finegrinding to a size below 0.1 to 0.2 mm.

In carrying out firing of raw materials in an apparatus of a shaft type,raw mixture or raw components may be placed into the shaft without anypreparation. If the raw materials are preliminarily pelletized beforeplacing into the shaft, aerodynamic drag of the raw materials layer issubstantially reducing owing to identical size of raw materialparticles; it also allows to simplify the sealing devices of gassupercharge and draft systems. In addition, more favorable conditionsfor the occurrence of reactions between components obtain within thepellets.

The batch according to the invention, as mentioned above, is capable ofhardening under autoclaving as well as under nonautoclaving conditions.Under autoclaving, product strength is enhanced. Additional lowering ofmaterial usage for production equipment can be achieved by carrying outa two-stage treatment of a product: first under atmospheric pressure atwater vapor temperature of 30° to 100° C. during 4 to 10 hours then inan autoclave at a temperature of, e.g., 115° to 200° C. during 3 to 6hours. This technique allows products of enhanced strength to be made athigh autoclave throughput capacity.

DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a preferred version of embodiment of aproduction line for manufacturing building products according to theinvention;

FIG. 2 shows a version of an embodiment of an shaft-type apparatuswithout a fire-proof lining for preparing a batch according to theinvention, which is incorporated in the production line of FIG. 1;

FIG. 3 shows a version of an embodiment of firing of a raw material massfrom the interior thereof.

EMBODIMENTS OF THE INVENTION

The best way of carrying out a process for making building products isimplemented by using a production line shown in FIG. 1. Raw material andfuel components are supplied to the production site by conventionaltechniques and are charged into storage hoppers 1, 2 and 3 for coal,limestone and clay, respectively. Coal or another solid fuel componentis supplied by means of a feeder 4 to a roll crusher 5 which grinds thecoal to a particle size below 2 to 3 mm, whereafter the coal is fed to ahopper 6. Limestone is supplied by means of a feeder 7 to a roll crusher8, and the cruched limestone of a size less than 5 to 10 mm is fed to ahopper 9. Clay (or loam) is fed by means of feeder 10 to coarse grindingrolls 11 and then to a disintegrator 12 for comminution, and the clay isthen fed to a hopper 13. Coal and limestone by feeders 14, 15 and by aconveyor 16 and clay by a feeder 17 are supplied to a mixer 18 havingdamper where the components are mixed and wetted to a moisture contentof 15 to 20%. The clay is supplied by a feeder 19 to a mixer 20 having adamper, where the clay is homogenized and wetted to a moisture contentof 15 to 20%. After mixers 18 and 20, the mass is supplied topelletizers 21 and 22 of any appropriate known type. The resultingpellets of 10 to 30 mm (the pellets from clay are preferably of asmaller size) are fed to conveyor driers 23, 24 in which their moisturecontent is lowered to 4 to 12%. Pellets from clay are supplied by anelevator 25 and conveyor 26 to a loading hopper 27. Pellets from mixture(of clay, limestone and coal) are supplied by an elevator 28 andconveyor 29 to a lading hopper 30. Feeders 14, 15, 17, 19 and conveyor16 work in such a manner that coal content in the pellets from themixture be from 2.5 to 4.5% by weight depending on caloric capacity ofcoal and limestone content be from 5 to 20% depending on other processparameters and the ratio of mass of mixture pellets to clay pellets ispreferably from 90:10 to 65:35. Hoppers 27, 30 are loading hoppers of afiring unit 31 which is shown in greater detail in FIG. 2. Mixturepellets are fired in firing unit 31 owing to the presence of coal in thepellets at a temperature of preferably 900° to 1100° C., and claypellets are heated up to temperatures below of said maximum temperatureowing to heat released from firing of the mixture pellets. After thefiring, clay pellets from a hopper 32 are crushed in a roll crusher 33and comminuted in a disintegrator 34 to a particle size smaller than 0.1to 0.2 mm and are fed to a hopper 35. After firing the mixture pelletsare supplied from hopper 36 by a conveyor 37 to an absorber 38 wherethey adsorb sulfur dioxide and also carbon dioxide from off gasesremoved from unit 31 through a smoke exhauster 39 and the gases are thenexpelled by a smoke exhauster 40, and the mixture pellets are dischargedinto a hopper 41. The components are then supplied by batchers 42, 43 toa mixer 44 having a damper for preparing a molding mass with a moisturecontent of 5 to 15% depending on molding method and equipment. Themixture is then supplied by a conveyor 45 to roll crusher 46 and then toa rotary crusher 47 for agitating and then to a molding mass hopper 48of a semi-dry press 49 in which brick or blocks are pressed at aspecific pressure of 15.0 to 25.0 MPa. An automatic charger of the pressremoves green brick from the press worktable and places it on a car 50which is moved to a chamber 51 of humid thermal treatment. This chambermay be in the form of a steaming chamber, or a low-pressure chamber, oran autoclave, where products are treated during 3 to 15 hours dependingon steam parameters. The resulting products have a strength of 10.0 to15.0 MPa and higher, frost resistance over 25 cycles, water absorptionof 12 to 17%. All components of the production line, except for unit 31,are well known and are used in the manufacture of building materials,and absorber 38 is used in the chemical industry. If a low-sulfur coalis used, this adsorber may be dispensed with, and the content oflimestone in the raw mixture can also be lowered in this case.

An embodiment of a firing apparatus shown in FIG. 2 comprises a shaft 52which is made, e.g., out of thin medium-grade steel sheet. The shaft hasin its top part a unit for separate charge consisting of a casing 53accommodating loading hoppers 27, 30 with batchers 54, 55 connected totheir drives, an intermediate hopper 56 mounted on posts 57, movablecones 58, 59 connected by means of tie members 60, 61 to drives, apartition wall 62 in the form of a ring attached to posts 63. The ringsupporting posts 64 on which a immovable cone 65 is mounted. Casing 53is connected to a flue 66 having a smoke exhauster 67. A unit forseparate discharge is provided under a discharge opening of shaft 52 andhas a drive shaft 68 with posts 69 supporting rotating discs 70, 71, 72mounted above one another. Lower disc 70 is continuous, and each of theother discs has a central opening. The diameter of discs 71, 72decreases in steps towards continuous lower disc 70. The diameter of thecentral opening of each disc 71, 72 also decreases in the same manner.Tripping scrapers 73, 74 are provided adjacent to discs 70, 71, andhopper 36 is mounted under the scrapers. A tripping scraper 75 ismounted adjacent to disc 72, and hopper 32 is mounted under thisscraper. The apparatus may have a larger number of the discs, eachhaving at least one scraper. Immaterial elements of the apparatus,including supports of the shaft, hoppers, scrapers, and drive shaft, asdevice for rotating the drive shaft (drive) are not shown as they mayhave various appropriate known modifications.

The apparatus shown in FIG. 2 functions in the following manner. Claypellets from hopper 27 are supplied by batcher 54 under the action of adrive into intermediate hopper 56. Tie member 60 is driven to raisemovable cone 58 so that clay pellets spill over cones 59, 65 into thespace between shaft 52 and cylindrical partition wall 62, whereaftercone 58 is lowering into its initial position. Mixture pellets aresupplied from hopper 30 by batcher 50 under the action of tie member anddrive (not shown) into intermediate hopper 56. Tie member 61 movesmovable cone 59 down, then the tie member 60 raises movable cone 58 sothat mixture pellets spill over inside partition wall 62, and then thecharging cycle is repeated. Firing of mixture pellets occurs in shaft 52owing to the coal available in the pellets similarly to a process in anormal shaft furnace. During the process the clay pellets are subjectedto the influence of temperatures (which are below the mixture pelletstemperature) decreasing in the direction towards the wall of shaft 52through heat transference from the mixture pellets. The temperatureacting upon the shaft wall depends on the duration of firing of themixture pellets at the maximum temperature, on the amount of spacebetween partition wall 62 and shaft 52 which may vary depending on thedesired composition of fired products and phases ratio and otherfactors, the space can be preferably of 40 to 100 mm. Smoke exhauster 67ensures optimum conditions of gases movement through the pellets layerdetermined following well-known rules. The pellets descend towards thedischarge opening of shaft 52 and are cooled with sucked air. The claypellets get onto disc 72 having the diameter of its central openingwhich is close to the diameter of partition wall 62. The mixture pelletsget onto discs 71, 70. During rotation of shaft 68 clay pellets aretripped by scraper 75 into hopper 32 and mixture pellets are tripped byscrapers 74, 73 into hopper 36 From the hoppers pellets are fed forfurther treatment as shown in FIG. 1 or for being otherwise used.

Devices for separate charging and discharging may be of any other type,provided they can perform the above described functions. The device forseparate charge may also be in the form of a double rotatable chutehaving one discharge opening located over the space between schaft 52and partition wall 62 and another opening located within the partitionwall 62. In this case the partition wall may be dispensed with if achute rotation mechanism is synchronized with a discharge mechanism ofthe schaft. Shown in FIG. 2 the separate discharge device is amodification of a prior art device 6! which was intended for differentpurposes. Another methods for separating mixture pellets and claypellets without using an separate discharge device, e.g., by preparingpellets of different size in pelletizers 21, 22, discharging all pelletsfrom the shaft, and screening the pellets into fractions. Since claypellets of smaller size are located adjacent to the shaft walls,spurious draft in this area decreases since the layer of pellets oflarger size in the central part of the shaft offers a lower aerodynamicdrag to the gas flow. As shown above, clay pellets and mixture pelletscan be comminuted together. In using the process according to theinvention for preparing Portland cement clinker simultaneously with thepreparation of an active hydraulic additive to the cement separatedischarge is not required either. In this case, a discharge device maybe in the form of any device generally used in shaft furnaces for theproduction of cement clinker.

In a shaft-type apparatus for firing raw materials use may be made ofdifferent energy carriers such as gas. Fuel burning devices are wellknown in the art. The shaft may be provided with one or several bottomburners located in the bottom part of the shaft, preferably at thecenter of its cross-section. The shaft may be provided with beam burnerspositioned on one or several beams, preferably in the central part ofthe shaft cross-section and in the vertically middle part of the shaft.A burner (or a plurality of burners) may also be provided in the centralpart of the cross-section of the top part of the shaft, a superchargedevice instead of a draft device being provided in the top part of theshaft in this case. This design allows one of the embodiments of the rowmaterials firing to be carried out in co-current.

The creation within the raw mass moving through shaft of a temperaturegradient directed into the interior of the mass can also be achieved byusing different techniques, e.g., by making gas permeable openings inthe shaft wall along its perimeter. Air admitted through the openingsowing to a pressure reduction provided by the gas exhauster counteractsthe thermal flux directed towards the shaft wall. The openings, whichare preferably controllable, may be made at different levels verticallyalong the shaft, the opening levels may corresponding to the position ofthe zone where the mass temperature is at its maximum.

One embodiment of the process for firing the mass from the inside isshown in FIG. 3. Clay from a hopper 76 is supplied to coarse gridingrolls 77 and disintegrator 78. Limestone from a hopper 79 is suppliedfor comminution into a roll crusher 80. The resulting components are fedto a mixer 81 having a damper in which the mixture is stirred and wettedto a moisture content of 15 to 20% and from which it is supplied to anextruder 82 for forming a tubular member 83 by means of a core 84 havingan internal axial passage connected to a draft device 85 to ensuremovement of a gaseous fluid through the interior of tubular member 83moving along a conveyor 86. A gas or other burner 87 is provided insidetubular member 83 on some depth. The temperature of heating of the innerpart of the tubular member is determined by the burner flametemperature. The temperature of the outer part of the tubular memberdepends on thickness of the member wall, temperature of the burnerflame, velocity of movement of the member along the conveyor, and otherfactors. Different-temperature phases of clayey substance are formedthrough the thickness of the member wall. Longitudinal projections orcavities may be provided on the inner and/or outer surface of tubularmember by providing a respective configuration of the die and core ofthe extruder so as to ensure an additional control of the ratio ofdifferent temperature phases in the fired product. Moisture from adamper 88 causes destruction of the fired member because of quenchedparticles of lime, and fragments of the member fall down into a hopper89. Several tubular members at a time may be formed.

The extruder may also form a clay member of tubular or like shape ofunclosed cross-section, and a longitudinal cavity is formed in suchmember into which a stationary heater may be inserted, e.g., an electricheater. The extruder may also form several rectangular-section (or like)members running in parallel with one another, the heaters beingpositioned in spaces between them. This technique is used to implementthe outer heating of the raw mass.

The heating of the interior part or preferably interior part of the massmay also be carried out using different technique principles, e.g., byusing high-frequency current for internal dielectric heating of the rawmass as it is used in firing clay for producing expanded clay with asuch difference that thermal action is carried out, e.g., in twomutually perpendicular directions, by placing around the raw mass twopair of plates of a pair of high-frequency capacitors.

The main rules dealing with methods for making choice of gradingcomposition of molding masses are well known and applicable to theimplementation of the claimed inventions.

I claim:
 1. A method for making a building product from products offiring a clay-containing material and products of processing alime-releasing material, which method comprises firing at least aclay-containing material up to at least beginning of its sinter,obtaining a molding mix comprising lime and products of firing aclay-containing material, molding a body of building product from saidmix, treating said body in a humid medium or in a medium containingwater vapor, characterized in that the products of firing aclay-containing material comprise a mixture of first and second portionsthat have been heated to respective first and second temperatures thatare different from one another, the two different temperatures beingwithin the temperature range from a temperature of beginning ofdehydration to at least a temperature of sinter of clay, so that theproducts of firing comprise both products of dehydration and products ofamorphization of clay, and further characterized in that the molded bodyis treated under treatment conditions selected from the group consistingof heating at a temperature of about 30° to 100° C., heating in asteaming chamber, treating in a low-pressure chamber, and heating in anautoclave at a sufficient autoclaving temperature of about 115° C.
 2. Amethod for making building product as claimed in claim 1, wherein theclay-containing material is being fired together with saidlime-releasing material, so as to obtain said products of firing aclay-containing material and lime, and products of such a firing areplaced before molding into the medium of the firing gases.
 3. A methodfor making building product as claimed in claim 1, wherein bothclay-containing material and lime-releasing material are together firedin co-current.
 4. A method for making building product as claimed inclaim 1, wherein through a firing the clay-containing material andcrushing product of this firing a ceramic sand is obtained which sandhas open pores, then a mixture containing said porous ceramic sand ismolded into the body of finished product under vibratory conditionsproviding that moisture leaves said process and afterwards a moistenedmass containing said at different temperatures fired products fills saidpores.
 5. A method for making building product as claimed in claim 1,wherein the body of finished product is treated first under atmosphericpressure at a temperature of about 30° to 100° C. during about 4 to 10hours and then in an autoclave at a temperature of about 115° C. for aduration of about 3 hours.
 6. A method as claimed in claim 1 whereinsaid first portion of the material has been heated to a temperaturebetween about 500° to 800° C. and the second portion has been heated toa temperature between about 880° to 950° C.
 7. In a method for making abuilding product from a clay-containing material, wherein the materialoptionally has a content of limestone or dolomite, the methodcomprising:a) firing the clay-containing material by heating to at leasta beginning of sinter of clay, whereby to form products of firing theclay-containing material comprising ceramics, b) forming a molding mixcomprising lime and the products of firing the clay-containing material,c) molding a body of building product from said mix, and d) moist curingthe body at a temperature preferably not exceeding about 200° C.; theimprovement wherein i) the products of firing the clay-containingmaterial are formed by mixing a first portion of the material that hasbeen heated to a first temperature and a second portion of the materialthat has been heated to a second temperature which is different from thefirst temperature, said first and second temperatures being in a rangefrom a temperature of beginning of dehydration to a temperature ofsinter of clay and being selected such that said first and secondportions have different chemical or physical properties from oneanother, and ii) the molded body of building product is cured at atemperature not exceeding about 115° C.
 8. A method for making buildingproduct as claimed in claim 7 wherein the products of firing are placedinto a medium of firing gases before molding said body.
 9. A method formaking building product as claimed in claim 7 wherein the molded body ofbuilding product is cured at a temperature within a range of about 100°to 115° C.
 10. A method as claimed in claim 7 wherein said first portionof the material has been heated to a temperature between about 500° to800° C. and the second portion has been heated to a temperature betweenabout 880° to 950° C.
 11. A method as claimed in claim 7, wherein thelime is present in the molding mix as an alkaline additive in an amountof about 2 to 30 weight percent.
 12. A method as claimed in claim 11,wherein the lime is present in the molding mix in an amount of about 2weight percent.
 13. In a method for obtaining a fired product from claycomponents for making building products mainly by moist hardening,wherein the method comprises heating a clay-containing material to atemperature of firing the material, the improvement wherein the materialis heated to a temperature of firing until a temperature gradient iscreated in the material with a first portion of the material beingheated to a first temperature and a second portion of the material beingheated to a second temperature which is different from the firsttemperature, said first and second temperatures being in a range from atemperature of beginning of dehydration to a temperature of sinter ofclay and being selected such that said first and second portions havedifferent chemical or physical properties from one another, and mixingsaid first and second portions.
 14. A method as claimed in claim 13comprising forming the clay-containing material into a bulk masscomprising said first and second portions, then heating the firstportion of said bulk mass to a maximum temperature of firing, whichmaximum temperature is preferably not lower than a temperature ofbeginning of sinter of clay, with said heating causing the secondportion of the bulk mass to be heated to a different temperature whichis below said maximum temperature.
 15. A method as claimed in claim 14wherein said bulk mass is heated from an interior thereof with thesecond portion of said bulk mass surrounding the first portion of saidbulk mass.
 16. A method as claimed in claim 15 wherein the secondportion of said bulk mass is subjected to a temperature below atemperature of beginning of dehydration of clay.
 17. A method as claimedin claim 14, wherein the clay-containing material is heated by (i)mixing the clay-containing material with a solid fuel component to forma mixture; (ii) forming pellets from the mixture, and (iii) firing thepellets by burning said solid fuel component in a kiln.
 18. A method asclaimed in claim 17, wherein the method comprising drying the pelletsformed in step (ii) prior to firing in step (iii), and wherein the kilncomprises a steel sheet.
 19. A method as claimed in claim 17, whereinthe solid fuel component is present in the pellets in an amount of about2.5 percent by weight.
 20. A method as claimed in claim 17, wherein thesolid fuel component is selected from the group consisting of coal,waste from coal recovery and thermal utility waste.
 21. A method asclaimed in claim 13 wherein said first portion of the material has beenheated to a temperature between about 500° to 800° C. and the secondportion has been heated to a temperature between about 880° to 950° C.